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<br />. <br /> <br />CONTENTS <br /> <br />Pag, <br />Planning procedures and hydrologic variables un__________________n______ 1 <br />Availability of data and the technique of analysis ________________________n__ 3 <br />Effect of urbanization on increasing frequency of overbank flow ______________ 7 <br />Local storage to compensate for peak flow increase _______________________u_ 11 <br />Sediment production _u_______________ .. ____M_______________n__________ 11 <br />Effect of increased peak flows on sediment yield _ _________. ______________n__ 15 <br />Water quality _______ u ___ .'_'_ _____________ ____0.._ _ __ ________________________ 15 <br />Selected references _________________. __ _ ___________________________________ 18 <br /> <br />ILLUSTRATIONS <br /> <br />. <br /> <br />Po.. <br /> <br />FIGURES 1-8. Graphs showing: <br />1. Hypothetical unit hydrographs relating runoff to rainfall, <br />with definitions of significant parameters ___~~__n_ 3 <br />2. Effect of urbanization on mean annual flood for a 1~square- <br />mile drainage :'l.rea ________ __n_____________n_____ 5 <br />3. Flood~frequency curve for partial-duration series, West <br />Branch Brandyine Creek at Coatesvi11e, Pa., based <br />on data for 1942, 1944-51 _________uuu__________ 6 <br />4. Regional flood-frequency data for the Brandywine Creek <br />basin, Pennsylvania ____________nn____________n 8 <br />5. Flood~frequency curves for a I-square-mile basin in <br />various states of urbanization __________nn_______ 9 <br />6. Increase in number of flows per year equal to or exceeding <br />original channel capacity (1-square-mile drainage <br />area), as ratio- to number of overbank flows before <br />urbanization, for different degrees of urbanization ___ 10 <br />7. Annual sediment production per square mile for urbanized <br />and natural areas _.__________________~__n________ 12 <br />8. Relation of sediment yield and discharge for an urban and <br />a rural or unurbanized area _____________n__n____ 13 <br /> <br />TABLE <br /> <br />. <br /> <br />TABLE 1. Increase in discharge as a result of urbanization in a 1-square~mile <br />area _____________________________~________________~_______ <br /> <br />P..., <br /> <br />4 <br /> <br />III <br />